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The Greenland Shark, Somniosus microcephalus(Bloch and Schneider 1801) has seldom been ob-served under natural conditions, and until this report,had been observed by divers underwater only rarelyin Arctic waters (Caloyianis 1998). This giant memberof the elasmobranch Order Squaliformes is a slowmoving, primarily deep water shark reaching at least6.4 metres in length (Compagno 1984), found in cir-cumpolar regions and in cold, deep water to depthsof at least 2200 metres (Herendorff and Berra 1995).Greenland Shark stomachs contain a wide range ofprey including marine invertebrates, fish and mammalsas well as terrestrial vertebrates such as Caribou Rangi-fer tarandus (Compagno 1984), and the role of this spe-cies as a predator, or primarily a scavenger, of marinemammals is controversial (Bigelow and Schroeder1953; Ridoux et al. 1998; Lucas and McAlpine 2002).

St. Lawrence River Greenland Sharks free of theocular copepod parasite Ommatokoita elongate wereobserved by divers during an unusual inshore migra-tion associated with seasonal concentrations of Cape-lin Mallotus villosus. Here we report on closely ap-proached sharks that exhibited display motor patternsnot previously described in this species.

MethodsWe employed SCUBA and underwater video in the

region of Baie-Comeau, Quebec, Canada (49°16.9'N,68°07.2'W, Figure 1), to record Greenland Shark size,sex, physical condition, swimming speed and behav-

iour in May and June 2003. The occurrence in in-shore waters of this elusive species was accompaniedby an unusually high seasonal inshore concentrationof Capelin (Mallotus villosus) massing around docksand bottom structures which was the highest recordedin the region over the previous five years (F. Gregoire,Canadian Department of Fisheries and Oceans, InstituteMaurice Lamontaigne, Mont-Joli, Quebec, personalcommunication 2003). Both juvenile Harbour Seal(Phoca vitulina) and Grey Seal (Halichoerus grypus),potential prey species of the sharks, were locally abun-dant and were observed during fieldwork and divingactivities.

Observations were made between 09:00 and 17:30Eastern Standard Time and occurred in seawater depthsfrom 10.0 to 28.0 m (mean=18.1 m +/- 5.8 m 95% con-fidence interval, CI). Seawater temperatures rangedfrom 1.0°C to 9.0°C (mean= 4.4°C +/- 3.1°C 95% CI).We employed a standard report form and interviewedlocal professional divers, who first reported the pres-ence of sharks in the region.

Videotape of sharks was analyzed for size scale usingadjacent objects of known maximum size (PlumoseAnemones, Metridium senile, maximum height of 40 cm) and visible time code (hours/minutes/seconds)to determine swimming speed. We recorded 68.2 videominutes during prolonged encounters with four sharksover a three-day period and documented six other en-counters occurring between 26 May and 12 June 2003in the same region.

Vision and its Relationship to Novel Behaviour in St. Lawrence RiverGreenland Sharks, Somniosus microcephalus

CHRIS J. HARVEY-CLARK1, JEFFREY J. GALLANT2, and JOHN H. BATT3

1Animal Care Center, University of British Columbia, 6199 South Campus Road, Vancouver, British Columbia V6T 1W5Canada, email: chclark@interchange.ubc.ca

2Aqualog Society, P.O. Box 483, Drummondville, Quebec J2C 6W3 Canada, email: aqualog@aqulaog.ca 3Aquatron Laboratory, Department of Oceanography, Dalhousie University, Halifax, Nova Scotia B3H 4J1 Canada; e-mail:

John.Batt@Dal.ca

Harvey-Clark, Chris J., Jeffrey J. Gallant, and John H. Batt. 2005. Vision and its relationship to novel behaviour in St. LawrenceRiver Greenland Sharks, Somniosus microcephalus. Canadian Field-Naturalist 119(3): 355–359.

Rarely observed Greenland Sharks, Somniosus microcephalus, were recorded at shallow depths by divers employing underwatervideo in the St. Lawrence River, in association with a seasonal concentration of Capelin (Mallotus villosus) in May-June 2003.We recorded unique proximity-induced display motor patterns in these sharks, which have not been recorded in underwaterobservations of Arctic Greenland Sharks. Arctic sharks have a high incidence of blindness due to an ocular copepod parasite,Ommatokoita elongata. The absence of parasite-induced blindness in St. Lawrence Greenland Sharks, in contrast to endemicblindness in the Arctic population, may allow sharks in this region to more readily visually recognize the presence of conspecificsand potential prey. Improved visual acuity may therefore allow St. Lawrence River sharks to express a different behaviouralrepertoire than Arctic sharks, with resulting changes in intra- and inter-specific aggression and predatory behaviour.

Key Words: Chondricthyes, Squaliformes, Somnosidae, Greenland Shark, Somniosus microcephalus, display behaviour, copepod,Ommatokoita elongata.

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Results Of the 10 shark encounters, the range in estimated

length was from 2.5 to 4.5 m total length (mean = 2.8 m +/- 0.34 m CI 95%). In four sharks sex wasdetermined (3 female, 1 male), with one markedly“girthy” 3.0 m female shark believed to be gravid. Inone instance three sharks were seen separately on thesame dive and in one instance two sharks were ob-served simultaneously within 5 meters of each other ondiverging courses. Shark swimming speeds rangedfrom 0.10 m/s to peak at 1.40 m/s (mean = 0.62 m/s+/- 0.31 m/s 95% CI). Greenland Sharks were capableof rapid acceleration from 0.10 m/s to 1.40 m/s andcould outpace divers when swimming in a straightline, were highly manoeuvrable and were capable ofchanging depth and direction rapidly. In one case, thesame 2.50 m female shark identified by scar patternswas seen repeatedly over a 3-day period in the samelocation, in each case within 50 m of the same posi-tion when encountered. Female sharks were noted tohave more scarring than males, generally linear scar-ring on the tail, pectoral fins and dorsum of the cau-dal peduncle. We postulate that these scars may haveresulted from nuptial or combat related behaviour, asobserved in other shark species (Compagno 1984).

Both sexes exhibited a whitish cruciate pattern whichappears to be a loss of pigmentation on the anteriorrostrum, and which may be the result of bottom for-aging activities using the rostrum (Figure 2). A maleshark was noted to have a single left clasper, althoughthis species generally possesses two claspers (Com-pagno 1984).

During encounters sharks were found swimmingapproximately 1.0 to 2.0 meters above the substratetowards divers on converging courses, and followingclose approach swam on sinusoidal courses, in somecases performing complete or half circle manoeuvresover a wide radius (20 to 30 m). These circling man-oeuvres resulted in sharks maintaining continuous eyecontact with divers, and in two instances sharks leftthe bottom to ascend upwards at an acute angle andclosely approach a diver above them in mid-water,apparently in investigative fashion.

When sharks were closely approached from thelateral or anterior aspect (2.0 m or less from the eye),they initially displayed a motor pattern which includ-ed rapid bilateral ventral deflection of the pectoralfins (Figure 3 a, b), deceleration, and adoption of a

356 THE CANADIAN FIELD-NATURALIST Vol. 119

FIGURE 1. Location of Greenland Shark sightings in the St.Lawrence River in the vicinity of Baie-Comeau, Prov-ince of Quebec.

FIGURE 2. The rostrum of a female Greenland Shark illus-trating typical loss of pigmentation seen anterior andadjacent to prominent nares. The cornea lackingattached parasitic copepods, and the dorsal opercu-lum are clearly visible.

FIGURE 3. Female Greeland shark showing (a) normal pectoral fin position and (b) marked ventral deflection of pectoral finsas part of a motor pattern observed consistently when closely approached by divers.

(a) (b)

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head-down attitude with the front of the animal 0.1-0.3 m above the substrate, the trunk slanted upward andthe tail held higher off the bottom, the dorsum curvedupward, the axis of the body being held approximately10 degrees off horizontal, and the mouth held slightlyopen (Figure 4). This posture was maintained from oneto several seconds, after which the shark would accel-erate and swim away from the diver or change courseto avoid the diver. This motor display was repeatedlyexhibited by the four sharks we observed when close-ly approached.

DiscussionArctic Greenland Shark populations have high

infection rates with the ocular copepod parasite Om-matokoita elongata (Grant, 1827), which has beenfound in up to 98.9 percent of individuals in surveyedpopulations (Berland 1961), and in 100 percent ofindividuals in a recent tracking study off Baffin Island(Skomal and Benz 2004). Based on histopathologicalfindings in copepod-parasitized eyes, Borucinska etal. (1998) postulated that sharks infected with ocularOmmatokoita were likely to be blind. However, thesharks we observed were free bilaterally of externalsigns and lesions of this parasite, had clear cornealepithelium, showed definite visual orientation to divers,tracked divers with horizontal and vertical eye move-ment, repeatedly demonstrated visual avoidance ofdivers and objects on the bottom, and repeatedly exhi-bited the described behaviour when closely approached.Vision is thought to be a major sense for investigativeand social behaviour, prey recognition and predationmotor patterns in the majority of shark species (Gruber1977). The visual acuity of the non-parasitized sharkswe observed in the St. Lawrence River may have pro-found implications for the social behaviour and pat-terns of predation of this population. The reason thesesharks have relatively low ocular copepod infestationrates compared to Arctic populations is unclear, andmay relate to parasite abundance and ecology, host fac-tors such as population density, nutrition and immunestatus, and/or environmental conditions such as dis-persion currents, seawater salinity and temperature.

Our perception of this species as a predator of benth-ic fishes and a sluggish, blind, olfactory scavenger ofmarine mammal carcasses, with an important ecologicalrole as a mammal “carcass opening” species in Arcticdeep water ecosystems (Snelgrove and Smith 2002)has changed as a result of these first-hand observations.Though descriptions of active predation by GreenlandSharks have not been reported in the scientific litera-ture, there is evidence that this species is capable ofactively stalking and killing marine mammals as wellas scavenging the carcasses of marine mammals. Ri-doux et al. (1998) documented a freshly killed juve-nile Ringed Seal, Phoca hispida (Schreber, 1775), withbite marks across the chest, found in the stomach of a4.5 m Greenland Shark off Iceland. Our underwater

observations support the contention that large, stealthyGreenland Sharks are capable of rapid manoeuvring,moderate speed swimming and potential predation ofinfirm, sleeping (Ridgway et al. 1975), or predator-naïve juvenile seals. This population of sharks is visualand can avoid or seek divers visually, and using othersenses in conditions of poor visibility, and we advisecaution when diving under low visibility conditions inareas where these sharks are known to occur. St. Law-rence River Greenland Sharks remain in the same shal-low water area for multiple days, repeatedly revisitnovel potential prey items in the environment, ascendfrom the bottom to investigate divers in mid-water,circle and maintain constant visual contact with diversrather than fleeing, and exhibit unusual motor displaypatterns when approached closely by divers. Thesefindings are consistent with the behaviour of a sharkspecies which has the potential to act as an oppor-tunistic predator as well as a scavenger.

AcknowledgmentsThe authors gratefully acknowledge the assistance

of Alain Simard, Jean-Yves Forest and Sylvain Sirois.

Literature CitedBerland, B. 1961. Copepod Ommatokoita elongata (Grant)

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Bigelow, H. B., and W. C. Schroeder. 1953. Fishes of the Gulfof Maine. Bulletin of the United States Fish and WildlifeService 53(74): 53-55.

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2005 HARVEY-CLARK, GALLANT, AND HART: VISION IN ST. LAWRENCE RIVER GREENLAND SHARKS 357

FIGURE 4: Male Greenland Shark posturing, exhibiting curva-ture of the dorsum, having just shown rapid downwardflexion of head and tail, contacting the silt-coveredsubstrate, which caused the visible cloudiness ahead ofand behind the animal. This motor pattern was elicitedin response to presence and close proximity of divers.

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Compagno, L. V. J. 1984. Sharks of the World. An annotatedcatalogue of shark species known to date. FAO FisheriesSynopsis 125. Hexanchiformes to Lamniformes 4: 103-105.

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Received 6 November 2003Accepted 10 May 2005

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